Spent Caustic Treatment

Transcription

1 Spent Caustic Treatment Industrial Wastewater Treatment Water Arabia 2015 Bryan Kumfer Copyright Siemens AG All rights reserved.

2 Introduction / Contents Overview Spent Caustic Background Spent Caustic Treatment Options Description of the Zimpro process Sulfidic Spent Caustic Treatment Mixed Refinery Spent Caustic Treatment Conclusions

3 Spent Caustic Background Sources What is the Spent Caustic? Spent caustic is a waste product generated by chemical and petroleum sweetening processes Spent caustic is produced during the production of high quality: Ethylene LPG Gasoline Diesel Kerosene Natural Gas Typical Spent Caustic Constituents Compound Concentration NaOH 1-5 wt% Carbonates 1-5 wt% Sulfides wt% Mercaptans wt% Phenols 0-3 wt% Naphthenics 0-5 wt% Chemical O 2 Demand g/l

4 Spent Caustic Background Classification Type Source Problem Compounds Most Significant Treatment Challenges Sulfidic Ethylene LPG Scrubbers or Natural Gas Sulfides Mercaptans Odor COD Cresylic Scrubbing of FCC gasoline washes Phenols and reduced sulfur Odor Biodegradability COD Naphthenic Scrubbing kerosene, diesel, and jet fuel Naphthenic compounds, phenols and reduced sulfur Odor Biodegradability COD

5 Spent Caustic Background Hazards Why is spent caustic difficult to dispose of? Safety Potential H 2 S release Extremely Odorous - Sulfides and mercaptan Low Biodegradability BOD:COD ratio often 0.3 or lower Toxic - Phenols in high concentrations Foaming Naphthenic acids in high concentration Oil Potential emulsified, free and or dissolved acid oils High COD - 10,000 to 250,000 mg/l COD

6 Spent Caustic Treatment Treatment Options What are typical spent caustic disposal options? Off-site Deep well Brokering to paper mill or alumina producer Recovery of cresylic and naphthenic acids Hazardous waste disposal On-site Incineration Acid springing followed by Biological Treatment in WWTP Biological Treatment in WWTP Wet Air Oxidation followed by Biological Treatment in WWTP

7 Zimpro Wet Air Oxidation A Siemens Technology World s Leading Supplier of Wet Oxidation Systems More than 50 years of experience with wet oxidation system design and construction Over 200 wet oxidation systems for a variety of applications Atofina, Rho Italy

8 Spent Caustic Treatment Zimpro Wet Air Oxidation Technology What is the Zimpro Wet Oxidation process? Oxidation reactions occur in the water phase Elevated temperature (spent caustic treatment ~110 to 260 C) Elevated pressure (spent caustic treatment ~1 to 90 barg) Air provides soluble oxygen for oxidation reactions Spent Caustic Before and After Treatment

9 Spent Caustic Treatment Zimpro Wet Air Oxidation Process Flow Diagram

10 Spent Caustic Treatment Wet Air Oxidation Treatment Temperatures Classification Temperature (Pressure) Treatment of Compounds Low C (1.5 7 bar) Reactive Sulfides Mid C (20 40 bar) Sulfides, Mercaptans High C (50 90 bar) Naphthenic and Cresylic Acids, Sulfides, Mercaptans

11 Spent Caustic Treatment Wet Air Oxidation Process Wet Air Oxidation Treatment of Spent Caustic Destroy reactive sulfides eliminate odor and H 2 S emissions Destroy or breakdown complex pollutants (phenols, cresylates, naphthenates) Generate effluent that is biodegradable and can be discharged to conventional treatment Reduce high COD load sent to downstream treatment

12 Zimpro Wet Air Oxidation Spent Caustic Treatment Number one industrial application for the technology More than 20 years of experience 48 spent caustic treatment systems supplied worldwide BASF, Port Arthur, Texas

13 Wet Air Oxidation Treatment of Sulfidic Spent Caustic Results From Laboratory Testing

14 Untreated Sulfidic Spent Caustic Characterization LPG Spent Caustic Sample Analysis Results Units Reported As Chemical Oxygen Demand mg/l O 2 62,700 Organic Carbon mg/l C 7,260 BOD: COD ratio Sulfide mg/l S 17,800 Total Mercaptans mg/l CH 3 SH 9,880

15 of Sulfidic Spent Caustic Reduced Sulfur Reduced Sulfur (mg/l as S) 5,000 4,000 3,000 2,000 1,000 0 Reduced Sulfur Concentrations in Effluent Low Temperature Mid Temperature High Temperature Low temperature effluent- Detectable mercaptans Mid and high temperature effluent No detectable mercaptans

16 of Sulfidic Spent Caustic Biodegradability 0.6 BOD: COD Ratio of Untreated Sulfidic Spent Caustic and Effluents Untreated Spent Caustic Low Temperature Mid Temperature High Temperature Results Based on 5 Day BOD Test

17 of Sulfidic Spent Caustic Biodegradability COD Consumption Trendplot for Feed and Effleunts corrected for seed and dilution phthalic acid std Oxygen Uptake, % of CODi Mid Temperature Effluent 20 Untreated Spent Caustic Elapsed Time, hours

18 of Sulfidic Spent Caustic Full Scale Case Study - Chinese Refinery System Information Mid Temperature System Treating Ethylene Spent Caustic Located in China Treatment Results Non Detectable Sulfide and Mercaptans Readily Biodegradable (>0.6 Biodegradability ratio) 93% COD Reduction Analysis Results Units Reported As Untreated Spent Caustic Effluent Chemical Oxygen Demand mg/l O 2 42,100 1,420 Biodegradability Ratio Sulfide mg/l S 17,500 <1.00 Mercaptans mg/l CH 3 SH <1500 <1 Thiosulfate mg/l S 2 O 3 2,580 <100

19 Wet Air Oxidation Treatment of Mixed Refinery Spent Caustic Results From Laboratory Testing

20 Treatment of Mixed Refinery Spent Caustic Untreated Spent Caustic Spent Caustics Characterization Mixture of Naphthenic and Cresylic Spent Caustic Analysis Results Units Reported As Analytical Results Chemical Oxygen Demand mg/l O 2 49,300 Organic Carbon mg/l C 16,500 Biodegradability Ratio Total Phenols mg/l C 6 H 6 O 1,990 Naphthenic Acids mg/l ,200

21 Treatment of Mixed Refinery Spent Caustic - Biodegradability Respirometer Biodegradability Results for Untreated and Treated Spent Caustic Biodegradability Ratio Untreated Spent Caustic Deep Neutralization Low Temperature Mid Temperature High Temperature Results Based on 10 Day Respirometer Testing

22 Wet Air Oxidation High Temperature Effluent

23 Treatment of Mixed Refinery Spent Caustic - Total Phenols Total Phenols Concentration of Untreated and Treated Spent Caustic 2,000 Total Phenols (mg/l) 1,500 1, <100 mg/l <100 mg/l 0 Untreated Spent Caustic Deep Neutralization Low Temperature Mid Temperature High Temperature

24 Treatment of Mixed Refinery Spent Caustic Foaming Foaming Index of Untreated and Treated Spent Caustic 16,000 Foaming Index (ml) 12,000 8,000 4,000 0 Untreated Spent Caustic Acid Neutralization Low Temperature Mid Temperature High Temperature

25 Treatment of Mixed Refinery Spent Caustic - Chemical Oxygen Demand COD Concentration in Untreated and Treated Spent Caustic Chemical Oxygen Demand (mg/l) 50,000 40,000 30,000 20,000 10, % Removal 18% Destruction 40% Destruction 72% Destruction Untreated Spent Caustic Deep Neutralization Low Temperature Mid Temperature High Temperature

26 Treatment of Mixed Refinery Spent Caustic - Full Scale Case Study Indian Refinery System Information High Temperature System Treating Sulfidic, Cresylic and Naphthenic Spent Caustic Located in India Treatment Results Non Detectable Sulfide and Mercaptans Total Phenols <100 mg/l Readily Biodegradable (>0.6 Biodegradability ratio) 78% COD Reduction Analysis Units Reported As Untreated Spent Caustic High Temperature Effluent Chemical Oxygen Demand mg/l O 2 48,100 10,200 Biodegradability Ratio mg/l O 2 < Sulfide mg/l S 770 <1 Mercaptan mg/l CH 3 SH 132 <1 Thiosulfate mg/l S 2 O <100 Phenols mg/l C 6 H 6 O 710 <100

27 Conclusions Wet Air Oxidation Eliminates safety concerns related to H 2 S release Eliminates noxious odors Produces highly biodegradable effluent Destroys difficult to treat naphthenic and cresylic compounds Reduces COD load for down stream sent to WWTP

28 Thank You! Siemens Energy, Inc 301 W Military Rd Rothschild, WI Bryan Kumfer Research and Development Manager Phone: 1 (715) bryan.kumfer@siemens.com